The Stovebolt Site Forums The Shop Area General Truck Talk Power vs weight

I’m trying to figure out how much engine torque I’ll need on my 1940 WB 1.5 ton to climb a 7% grade without having to keep shifting down until I’m going 25 in second gear wound out redlining up the mountain.

The reason is because I live in the country and between me and pretty much everywhere else there is a 7% mountain that’s 5 miles up one side and 4 miles down the other. I would like to be able to maintain at least 45-50 the speed limit on the mountain is 60. I have no idea what my 1.5 ton weighs... I think read somewhere it should be around 5k. It has the 216 and crashbox but I have a 261 and sm420 that should work much better, but I’m worried it still won’t be enough. Gears are currently 6.17 but I’ll be swapping them for 5.43s.

Truck is not on the road yet so I haven’t tested the 216 vs the mountain.

Thoughts?

Will your truck be loaded or empty?

My 1957 Fire Engine weighs 14,400 with out any water in the tank and with a 200 hp V8 I drop down to about 40-45 mph when topping out on a long grade and that's if I hit the grade doing about 65-70 mph first (7-8% grade 5 miles long). Things really drop off fast if I have to tap the brakes for any reason.

Mike B

Mostly empty.

Chevy used NP 540 transmission in some big bolts, I've got one in a `60 C60.
5th is direct, 4 fills the 3 - 4 gap on most truck 4 speeds.

I put an NP-540 in an early Bronco, much better than the 3 speed, 55 or 60 in 4th with a load, then drop to 5th when on level, just like above.

Ed

That 3-4 gap is a killer with a 216 and a crashbox, there is literally nothing you can do to up or down shift that trans fast, so every time you lose speed and then lug the 216 which as we all know doesn’t have low end torque...

Since your not worrying about staying original, why not drop a 350 V8 in? They are dirt cheap at about $1600 new (Jegs, Summit, etc.) and can make 250 hp and 300 lb ft torque (the 261 has 150 hp & 230 lb ft torque for comparison). Couple the V8 to the SM-420 and go up the hill with the rear you have! Fitting exhaust manifolds might be the only real issue...

Just a thought...

Mike B

I may end up doing that. I’d like to make enough power with the 261 but from what I’m reading online it may not suit my needs.

I’d love to install something old school like a 348/409 but those are expensive and hard to find.

A stock truck 348 will only make about 175 hp...dollar for dollar you can't beat a SBC...brand new with a warranty for $1600 is hard to look past.

Mike B

280ish hp from a junkyard LS that will bolt right up....just sayin hahaha. They are the SBC of the 2000’s.

Might have to upgrade the radiator with a V8.

Ed

Needs a new radiator anyways! I only drive it on the gravel backroads for now because it’s not street legal yet and it heats up pretty good not boiling over, but gets hot because the radiator is blocked. I forget which but I touched the top and the bottom one was super hot the other was cool to the touch and that was only a 3 mile drive on country roads.

The 216 reaches its peak torque at approx 1100 rpm. From 800 to about 1600 the torque curve is fairly flat, then it starts to drop off at higher speeds. So between 800 and 1600 is the "torque band" for that engine. See performance curves for 1940 here:
http://chevy.oldcarmanualproject.com/chevyresto/4041.htm
An engineering analysis of your question is fairly complex... But the Chevrolet engineers considered those types of situations when they designed the trucks. Things like Rimpull, etc. Somewhere on the net, maybe Brad Allen has it, is a Truck Salesman's filmstrip guide to "sizing" trucks for the customers' needs. Other than that you'll have to learn from others' experiences.

If you want to keep a straight 6 look at a 292 with performance upgrades. It'll make more power than a stock 350

Would a 292 use much more gas and be more expensive to buy than a 350?
Would a 292 be easier to fit in the engine bay?

That odd "tall-straight look" might appeal to some viewers who might not know a stovebolt-six?

GMC 270/302 would be other more powerful closer-looking engines?

At what elevation? Tire size and gears will be a major factor.

John

2700 ft. Tires will be 8.25x20, 39 inches tall. Gearing is now 6.17 but will be changed to 5.43.

I have a 56 8400 wrecker that has a very mild 2-barrel 350 with the SM-420 and it will run 70 mph on the flat all day long, but it's probably turning in the upper 3000's rpm wise. So before you go to the trouble to change the rear gears, try out your new engine/trans first.

Mike B

The 292 is a torque monster.

GMC and later Chevies(292) are slightly longer, so engine compartment will have to be altered.

I agree with MikeB, try out existing gears first.

Ed

Nice truck, it looks pretty solid. I'd be concerned about keeping my downhill speed under control after getting to the top of one of those long grades.

Have you thought about a two speed rear end from an early 40's, 50's. They are loads of fun and that way you can keep the 216 for a while, it buy's you time. Our old 65 Chevy straight job 292 (6cyl) is a blast. At least I think it's a 65?